Strand supply apparatus



March 7, 1944.

P. J. KNAUS ETAL STRAND SUPPLY APPARATUS Filed Jan. 10, 1942 m m m u a wvmms I? d. ffl/A us 5 W inst/v M Z Aim/Mfr Patented Mar. 7, 1944 UN'iTsEE S TRAND SUPPLY .APBARATUS Peter v.J linans, .flinsdale, ,a-nd ,Einer .W. Larsen,

,lllmh rst, $1.11,,

Company,"'Inc0rp0ra-t ,poration of New;;York' assis t Wes r Ele t i AppiicationJanuary 10, 1 9%2, ;Serial No. 426,,300

5 Claims.

This K invention 1 relates .to a strand :supply lop.-

:;paratus and more particularly $058411 apparatus having :a torque motor brake for-"restraining 5a strand supply reel.

..It is; often-desirable, :when' transferringstrand cient tension-on. the strandmto-keep' it; tautat .all

.times. ,Mechanical: brakesqhavebeen .used here- :tofore to provide. a .tensioning means, but they tend toibecome uneven in operation. It is tan-obj ectvof the: present inventionto provide. an; efficient and effective;,appara'tus rior restraining; a supply reel for strand; material.

.In ,1 accordance with this object, a': torque -.inductionmotor may. be connectedwtora: supply reel byia suitablezmeans;such-.asa belt-the strand on thesupply reel being MIIWOUIld'Lby thewmaohine awhichv it' supplies and currentrbeing applied-ate the motor insuch away, as: to producea braking action, on the supply reel.

.; conjunction with the 1 accompanying drawing,

wherein Fig. 1 represents a side,elev,ation, of aitorque induction motor, connected" to a; strandesupply reel;

.- Fig.2 is a graphic representation pithespeed torque: characteristics-10f inductionamotors L-With ridifferent secondary resistances and Fig. 3 shows-schematically a; circuit'remployed in accordance-with this invention.

Absolutely .un-if-orm strand .tension. is: note re- ;quired: for most :strand .treating apparatus-rib :being; satisfactory :if the" tension remain (within relatively broad limits; 11112113515, thetensiommust not; be so great; as :to. stretch the strand @nor, on the otherhand, so-slight as to permit slackness. Becauseofgthe torque speed performance of cer--' tain types of torque induction motors when run in reverse against their field, as will be hereinafter explained, a substantially constant and uniform tension may be obtained on the strand by means of this invention.

It has been found that it is possible to obtain a definite torque speed characteristic in a torque induction motor by selecting a certain resistance for the rotor or secondary of the motor. By using a higher resistance in the secondary, the

torquerspeed G N/.61 tends to :flatten; using .a re- ;s-istance;of2 lower-,yalue on theother=hand,, gives uagtorque speed characteristic: in which the torque tends to increase very sharply as soon ,-.as ,t he

5 speedof the -motor isreduced, below synchronous :sp e *a'l :tor ue .t-may ma t 1 reach m imum a any s eed eme l y e ec in a ;-pr per resistance for the secondary. Since. the a l0B1;: c ntro -t t q spee qha tlota terist whe -the; moto d v i v tsa.

:well .as whe t i opera ed: w rd. it .wi vb .rse n th t itabl Y t qu p e -4 char ter st -to the motor :o eratin i 1. ve m b 2 tamedz n s e t n s ista cs a u tabl val lmth em o iment-ot th inv ion i lu r te in;-=Fig.; 1,-.a multiphase; vor three-phase; torqueiniI UCfiQnlm QI 510i. s itab an -c tyi shq having a shaft 6 and a pulley l moun ted pn this ;shaft. --'-Il r;1e ;pul ley,1- is driven by a pulley I3,

FCQQILBCtS QhGPWO pulleys and the slia ft ll acts .1 a. suprm t- I nasupn v s z; h c is su r se e t ere o Ais mn 4. -is-wolmd t rsu p vr el: and :ismul e t rou a, v sfi i is ap- 5 at. :substantially'constant speed; by the-capstan -:::-moic H A s a si s; round t ce fie tf h :istrand: isled ve dry-i s ea es ll ;,-.b t th min te s. an t enc ttoa: su ab 'tek wame swo d m- F{ig.;.2. shows; the. effect on the vtorque, speed .eharacteristi i a i d ctionm tono u ing. re- ;sis an es of.--d fi en v l es th -seconda y. of t,he.:mOtOI. Curve: 2| shows that a relatively low resistanc ives @a-m Ximu t qu a a s ed -.-;J' u st below synchronous speed. Qurves 22- 26 :show that s t nc sofhi e .va uaare us :in the; second ryr maximum mo gue is, btained e tlowe mo or. spe dsurve. 2 ho s a t rqu la. speed chara terist .w ere the u v v f 1 a rel at yely.1oware istam v i the con a i s: a s ardus -spee z har steristic in re r w ere abet-wee zSPfiQCL f;;..6 1M synchr n m i werseranda iiip fidfif, 0 V syn hro ise rsverse. unlik t que. drops. from; .inchz'nounds, to. 1 inchpounds.

While only six curves have been shown, it will be understood that the range of torque speed characteristics which are available is quite extensive and is dependent, within practical limitations, only on the resistance used in the secondary of the motor. When using a low resistance motor in reverse it will be necessary to employ a larger motor than would normally be selected for a given power requirement so as to prevent overheating. In Fig. 3 a three-phase induction motor 5, such as used in accordance with this invention, is illustrated having external resistances 30 connected to the secondary thereof. It will be understood that the motor may be so constructed, however, as to have the required resistance inherently.

The problem sought to be solved by the present invention was that of maintaining a substantially uniform and constant tension on a strand as it was unwound from a supply reel. This required a braking action on the reel which would decrease as the radius of the strand take-off became smaller. This will be apparent when one considers that, as the strand take-off radius became smaller, any rotative or counter-rotative force applied to the reel would have an increasingly greater effect on the strand. Thus, if the torque exerted by the braking motor remained constant at all speeds, then, as the take-oil radius of the strand became smaller, the tension on the strand would increase proportionately. This might well resultin stretching or even breaking the strand.

Since the strand is unwound at a substantially from the change in the radius of the strand take-"- off may be obtained; thus, a substantially constant and uniform tension may be obtained on the strand.

In one instance of an embodiment of this invention, a supply reel was used having a 9" inside diameter and a 12" outside diameter. Using a constant strand speed, it will be obvious that in the course of unwinding from a full reel to an empty one, the reel speed will increase one-third. Similarly, the tensioning effect of a given braking force applied to the reel will be increased by one fourth on the strand as a result of the change in the radius of strand take-oil. Thus, a torque speed relationship in the braking motor must be selected, by using a suitable resistance in the rotor, in which, over the range of speed of reel rotation to be used, the torque will be reduced by one-fourth as the speed is increased by onethird. Using a strand speed of 1300 feet per minute, a full 12" reel will rotate at approximately 414 R. P. M. An empty 9" reel would rotate then at approximately 552 R. P. M. It has been found that by using a torque induction motor of suitable power with a suitable resistance in the rotor, a torque speed relationship may be obtained which will give a substantially constant and uniform tension of any required strength on the above strand throughout the range of reel rotation speed employed; curve 2| in Fig. 2 shows ,a torque speed characteristic which may be used with a supply reel of the size indicated and over the speed of reel rotation indicated. It will be seen there that as the speed of rotation is increased one-third, that is, from 60% to of synchronism in reverse, there is a decrease in torque of 25%. This decrease compensates for the decrease in size of the radius of strand takeofi and consequent increase in leverage and results in a substantially constant tension on the strand.

While several embodiments of the invention have been described, it will be understood that many other applications are possible and that changes and modifications may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. A brake for applying a countenrotative force to a rotating object comprising a three-phase torque induction motor, having a rotating field, a rotor connected to said rotating object, resistances connected to said rotor to provide a suitable torque-speed characteristic and means for driving said rotor in reverse against its field.

2. In a strand unreeling apparatus, a strand supply reel, means for withdrawing strand from the reel, mean for applying a counter-rotative braking force to the strand supply reel comprising a three-phase torque induction motor having a rotating field, a rotor connected to said reel driven in reverse against its field by said reel, and a resistance connected to said rotor to provide a suitable torque-speed characteristic.

3. In a strand unreeling apparatus, means for unreeling a strand at a substantially constant speed, a supply reel for said strand, and means for applying a constant tension to said strand, comprising a multi-phase torque induction motor having a suitable resistance in the secondary and driven in reverse against its field by said reel to exert a counter-rotative force thereon.

4. In a strand unreeling apparatus, a rotatably mounted supply reel for the strand, a multiphase torque induction motor having a resistance in the secondary of suitable value to give a torque speed relationship when the motor is driven in reverse against its field which will produce a substantially constant tension on the strand, and means for connecting said reel and said motor in driving association.

5. In' a strand unreeling apparatus, means for unreeling a strand at a substantially constant speed, a rotatably mounted supply reel, a multiphase torque induction motor, means for connecting said reel to said motor so as to drive said motor, said motor having a suitable resistance in the secondary so that as the size of the radius arm of the strand take-off decreases, and consequently the speed of rotation of the reel increases, the torque of the motor will decrease so as to exert 'a decreasing braking or counter-rotative force on the reel and thereby maintain a substantially uniform tension on the strand.

PETER J. KNAUS.

EINER W. LARSEN. 

